Liquids subjected to analysis in some instances contain sediment or particulate contaminants which interfere with the qualitative and/or quantitive tests performed on the liquid sample. In some situations, such as the analysis of biological fluids, particularly body fluids such as urine, it may not be necessary to totally eliminate all particulate contaminants, but merely to reduce the amount of such contaminants to below the level or amount which interferes with the particular test being performed. Current practice accomplishes such a reduction in concentration of particulate contaminants with a variety of devices and associated techniques. Most of the devices and techniques involve drawing or passing the liquid sample (specimen) through a course filter which permits passage of purified liquid (filtrate) through the filter, the filtrate being drawn off from the downstream side of the device, while the particulate contaminant is retained on the upstream side of the filter. In some of these devices, the filter is discarded after transfer of the liquid component of the sample. With other devices used for such purposes the entire device is disposed of after use.
Some of these devices have shortcomings associated with the manner in which the device is manipulated or liquids are transferred. For example, introducing a sample at an upstream side of the device and removing filtrate from a downstream side of the device permits several potential sites of leakage. Additionally, with some of the devices, additional pieces of apparatus are required to successfully complete the transfer of filtrate. Many of the devices currently employed are also difficult to manipulate by all but those with above average dexterity. Furthermore, many of the techniques and devices currently employed require multiple steps which increase both the amount of time spent in transferring material and the potential for losses and contamination occurring during transfer and disposal of material.
The present invention permits facile sampling, reduces transfer problems, and reduces the potential for contamination of the sample while removing a substantial amount of particulate contaminant from the liquid, retaining the trapped particulate material in the device, and providing filtered liquid with reduced particulate concentrations. The devices perform the sampling of liquid specimen, separation of particulate contaminant from the liquid component and transfer of the substantially particulate-free liquid using a single piece of equipment, which is disposable, in essentially a single, continuous operation.